Adolfo Rodriguez <[email protected]> writes: > I am trying to use PETSc to solve a non-linear problem. The problem I am > facing is that I already have the Jacobian matrix formed in CSR format. Now > I am trying to define a function FormJacobian which takes this preexisting > matrix and writes it in PETSc format. For a small problem, I can use > MatSetValue, looping over all non-zero elements one at a time. However, > this turns out too slow for larger problems.
Best to call MatSetValues once per row. If the matrix is preallocated, it should not be slow. Check https://www.mcs.anl.gov/petsc/documentation/faq.html#efficient-assembly > In my current implementation, I am using MatCreateSeqAIJ which works great. > However, this approach does not seem to work to set the Jacobian. > > Any suggestions? > > Regards, > > Adolfo
